1. Field of the Invention
The present invention is related to ultrasound imaging and elasticity measurement for conventional ultrasound scanners.
2. Description of the Related Art
The measurement of tissue elasticity is very important in different clinical fields, such as assessment of liver fibrosis caused by various liver disease, scarring caused by burn, tissue fibrosis caused by radiotherapy, muscle stiffening caused by contraction and fatigue, etc. Consequently, various techniques for measuring tissue elasticity have been developed, for example, U.S. Pat. No. 6,494,840 teaches a tissue palpation device based on ultrasound indentation technique for quantitative measurement of tissue elasticity. By using an ultrasound imaging probe together with ultrasound indentation measurement, tissue elasticity can be measured with the guide of ultrasound imaging.
However, the palpation device has a number of limitations, including the requirement of tissue boundary condition. For instance, tissue needs to be directly compressed and requires an underlying tissue boundary. Also, the device can only provide an average elasticity valued for the entire tissue being compressed.
Another technique has been developed using static compression to show elasticity distribution in the tissue using strain imaging, for example, as disclosed in U.S. Pat. No. 5,107,837. Also, another technique has been developed using a vibration source and Doppler tissue velocity detection to map elasticity distribution, as discussed in U.S. Pat. No. 5,099,848. Furthermore, a number of approaches have been developed that uses vibration or acoustic radiation force to generate shear waves in tissues while using high frame rate ultrasound to monitor the propagation of the shear wave so as to measure or image tissue elasticity.
By using the foregoing methods, using vibration and radiation force, the intrinsic values of elasticity such as Young's modulus can be measured. However, there is still a need for simultaneous elasticity measurement and ultrasound imaging using conventional ultrasound imaging device.